JP2000054966A - Packing device for plunger type pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent plunger's abrasion caused by mineral particles which are assumed to leak, and enlarge life of a packing device. SOLUTION: In packing elements 29, 31 inserted into a sliding portion between a plunger 8 and a cylinder, a vector of a liquid pressure P acting to any point on the outer surface of a part near a sliding portion directs outside in relation to the central line of the plunger. When the vector directs inside, an angle made between a surface orthogonal to the axis and the vector is larger than 60 deg.. High pressure fluid in a pump chamber infiltrates through between a plunger surface and the packing element 29 and therefore leaks in principle, but mineral particles such as cement particles contained in the fluid between them do not scratch the plunger surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packing device for a plunger type pump, and more particularly, to a packing device inserted between a plunger and a plunger casing of a jet grout pump used for injecting a ground improvement agent into the ground. The present invention relates to a packing device for a plunger-type pump provided with a packing.

[0002]

2. Description of the Related Art Ground improvement has been carried out in various places for soft ground and the like. Ground improvement is implemented by inserting an injection device that injects a soil improvement agent into the drilling formed in the ground to be improved by boring, and injecting the soil improvement agent into the ground from the wall surface of the drilling by the injection device. . The main component of the soil conditioner is cement milk. A high-pressure pump is used for injecting cement milk. With the improvement of the ground improvement method, there is a demand for higher pressure of the high pressure pump. A plunger pump or a plunger compressor is used as a high-pressure pump that requires high-pressure compression.

[0003] The history of the development of plunger pumps for jet grout, which is required to output a high pressure, which is also referred to as an ultra-high pressure, has been a history of combating wear of the valve body. As the life of the valve body has been extended, the struggle has shifted to the struggle with the wear of the packing. In particular, wear of a packing mounted on a sliding portion where a plunger and a cylinder slide with each other is a problem.

[0004] A solution to such abrasion is known from Japanese Patent Application Laid-Open No. Hei 9-1558837 proposed by the present applicant. This known means uses U packing on the high pressure side,
A gland packing having a rectangular cross section is used on the low pressure side. Such a means has achieved the purpose of extending its initial life. The operation / effect is described in the paragraph number [001].
9] is explained as follows.

The U-packing, which has a small radial compressive force and easily recovers the adhesion to the plunger, has a large pressure drop effect on the low-pressure side, that is, on the rectangular packing side. For this reason, the fluid pressure entering between the rectangular packing and the plunger is low due to the head effect on the high pressure side of the U packing. U packing which receives high pressure radially inward
Good resilience and relatively long life for low pressure packing.
Further, the U packing is hardly worn due to its structure. It is susceptible to abrasion due to its large radial compression ratio, but it is difficult for dirt, fine particles, etc. to enter the sliding surface of the reduced-pressure rectangular packing. So it is hard to wear.

[0006] Such an estimation, which states that the wear is unlikely to occur, is based on the following confirmation of the performance of a practical machine.
In some respects it seems right. That is, the pressure between the plunger and the packing that slides with the fine particles of cement milk therebetween is small, and the liquid leakage is small because the pressure contact force between the plunger and the packing is relatively small. , That estimate is correct.

If the pressure is dynamically increased, the leak rate of the amount of leakage from a pinhole having the same size as the flow rate of the high-pressure fluid is expressed by exp (-kP), where P is the pressure. Attenuate with the coefficient This is because the wedge effect by the jet flow is enhanced between the inner surface of the pinhole and the leaked fluid. If the degree of pressure increase exceeds a certain threshold, the higher the pressure, the less the leakage will affect the lower pressure of the pump. Therefore, it is preferable that there is a gap between the rectangular packing and the plunger to some extent, and it is only necessary to prioritize that fine particles in the gap do not damage the plunger or the packing. The leak looks ugly to the eye, but technically it doesn't matter. Therefore, there is no problem with the rectangular packing. However, the following problem arises.

[0008] The fine particles caught under high pressure between the U packing on the high pressure side and the plunger damage the packing or the plunger. FIG. 7 illustrates the recently discovered plunger damage. The U packing 01 disposed on the side close to the pump chamber is provided with a high pressure P of the pump.
Immediately upon receiving this, it is strongly pressed against the plunger 02. The fine particles 03 sandwiched between the U packing and the plunger pressed against each other by this pressing force strongly press against the peripheral surface of the plunger,
It is presumed that the metal is subjected to the same abrasion effect as the metal is polished with a sandpaper, and a scratch appears there.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a packing device for a plunger type pump which prevents the plunger from being worn by mineral particles.

Another object of the present invention is to provide a packing device for a plunger type pump which prevents abrasion of the plunger by mineral particles without substantially reducing the discharge pressure.

Still another object of the present invention is to provide a packing device of a plunger type pump which can extend the life of the packing.

It is still another object of the present invention to provide a packing device for a plunger type pump which can extend the life of the packing and the plunger.

Still another object of the present invention is to provide a packing device for a plunger-type pump which can prevent abrasion of a plunger due to mineral particles or the like on the premise of liquid leakage and extend the life of the packing. is there.

[0014]

According to the present invention, there is provided a packing device for a plunger type pump, comprising: a plunger; a cylinder for sliding the plunger in the axial direction of the plunger; and a sliding member between the plunger and the cylinder. A packing group including a packing element inserted into the portion, a packing device of a plunger type pump used in a plunger type pump for increasing the pressure of a liquid containing mineral particles, wherein the packing group is radially attached to a sliding portion. The vector of the pressure of the liquid acting on any point on the outer surface of the part close to the plunger includes a packing element directed outward with respect to the center line of the plunger.

The pressing force of the packing against the plunger on which the high pressure in the pump chamber acts does not become extremely large.
Rather, the mineral particles that the high pressure fluid forcibly breaks with the fluid between the packing and the plunger do not press against the plunger surface. Since the high-pressure fluid itself is a coolant and a lubricant, wear of the packing is prevented. It is more effective to form the outer surface of the packing element at least on the high pressure side in the axial direction of the sliding portion.

A packing device for a plunger type pump according to the present invention includes a plunger, a cylinder for sliding the plunger in the axial direction of the plunger, and a packing element inserted into a sliding portion between the plunger and the cylinder. A packing device for a plunger type pump used for a plunger type pump comprising a packing group, wherein the packing group has a vector of a liquid pressure acting on an arbitrary point on an outer surface of a portion close to a sliding portion in a radial direction. When going inward with respect to the center line of the plunger, when an angle between the vector and a plane orthogonal to the center line is represented by θ, θ>
Includes a packing element that is 60 degrees.

When the angle θ is in such an angle range, the pressing force for pressing the packing against the plunger by the high-pressure fluid is reduced, and the above-described operation is effective. Also in this case, it is more effective that the portion close to the sliding portion in the radial direction is a portion on the high pressure side in the axial direction. Angle θ
May be constant, for example, preferably 90 degrees.

According to the present invention, there is provided a packing device for a plunger-type pump, comprising: a plunger; a cylinder for sliding the plunger in an axial direction of the plunger; and a packing element inserted into a sliding portion between the plunger and the cylinder. A packing device for a plunger type pump used for a plunger type pump comprising a packing group including: a side surface of an outer surface of a portion close to a sliding portion in a radial direction is orthogonal to the center line. The operation of this packing device is as described above.

In the above invention, it is particularly preferable that the leaking liquid is returned to the suction side of the pump chamber. In a packing device for a pump on the premise of leakage, environmental pollution can be prevented by returning leaked liquid to the suction side of the pump chamber. By providing a U-shaped packing at the end, it can be prevented from leaking out of the flow path system at all.

[0020]

FIG. 1 is a sectional view showing an embodiment of a packing device for a plunger type pump according to the present invention.
A crank mechanism 2 is provided in a crank casing 1. The reciprocating body 3 reciprocates by sliding on a sliding surface formed on a part of the crank casing 1. The eccentric rotator 4 and the reciprocating body 3 of the crank mechanism 2 are rotatably connected by a swinging and reciprocating crank rod 5.
A main casing 6 is firmly connected to the crank casing 1 in the axial direction.

A packing case 7 containing a packing group, which will be described later, is inserted into the main body casing 6 as a cylinder from the front end side thereof in the axial direction and firmly fixed to the main body casing 6. A plunger 8 is inserted into the packing case 7. The rear end of the plunger 8 and the reciprocating body 3 are firmly connected by a connecting rod 9. A liquid leakage prevention device 11 is provided on a joint surface between the crank casing 1 and the main casing 6.

A discharge side pump casing 12 is firmly joined to the front end face of the main body casing 6 and the front end face of the packing case 7. In the discharge side pump casing 12,
The suction side pump casing 13 is firmly connected.
The discharge-side pump casing 12, the suction-side pump casing 13, and the plunger 8 form a pump chamber 14 that expands and contracts.

A suction side valve device 15 is provided on the suction side pump casing 13 on the suction side of the pump chamber 14. The suction-side valve device 15 includes a suction-side fixed valve seat 16 fixed to the discharge-side pump casing 12 and the suction-side pump casing 13, and a suction that reciprocates and vibrates in opposition to the suction-side fixed valve seat 16. And a side movable valve element 17.

A discharge side valve device 18 is provided in the discharge side pump casing 12 on the discharge side of the pump chamber 14. The discharge-side valve device 18 includes a discharge-side fixed valve seat 19 fixed to the discharge-side pump casing 12, and a discharge-side movable valve body 21 that reciprocates and vibrates in opposition to the discharge-side fixed valve seat 19. ing.

The fixed valve seat 16 on the suction side and the movable valve body 1 on the suction side
7, the discharge-side fixed valve seat 19 and the discharge-side movable valve element 21
Since each is formed symmetrically before and after (before and after in the direction of flow of the liquid), it can be used by reversing the front and rear sides,
It is designed so that its durable life is doubled compared to one using only one side.

FIG. 2 is an enlarged view of a part of FIG. 1 showing the details thereof, and mainly shows a packing group between the packing case 7 and the plunger 8. The periphery of the plunger 8 is a high-hardness cylindrical body 22 made of an alloy material having high hardness and high wear resistance. The packing case 7 is provided with a front packing holder 23 from the front end side and a rear packing holder 24 from the rear end side.

The rear packing retainer 24 and the packing case 7 are screw-fitted with each other.
Can be propelled in the forward direction with respect to the front packing retainer 23. When replacing the packing group, pull out the rear packing retainer 24 from the packing case 7.

The packing group 25 is provided between the packing case 7 and the plunger 8 in the radial direction, and in the axial direction, the front packing holder 23 and the rear packing holder 24.
It is interposed between and. A leak liquid recovery ring 26 is interposed between the rear end of the packing group 25 and the front end of the rear packing holder 24 and between the packing case 7 and the plunger 8. A peripheral groove 27 for collection is formed in the leak liquid collection ring 26. Collection circumferential groove 27
Is connected to the collection plug 28.

The packing group 25 includes a plurality of elastic packing elements 29 and a plurality of rigid packing elements 31. The elastic packing elements 29 and the rigid packing elements 31 are arranged alternately in the axial direction. Both ends of the packing group 25 are rigid packing elements 31.
It is formed with. As a material of the elastic packing element 29, a polyamide resin is preferable. Rigid packing element 3
As the material for (1), a metal is preferable.

At the front end of the rear packing retainer 24,
An auxiliary packing 32 is provided. Auxiliary packing 32
Is fitted into a peripheral groove formed on the inner surface side of the rear packing retainer 24 and slides in contact with the outer peripheral surface of the plunger 8. The auxiliary packing 32 is a low pressure packing, and is preferably a U packing.

The cross-sectional shapes of the ring-shaped elastic packing elements 29 and the rigid packing elements 31 shown in FIG. 2 are rectangular. The side surfaces on both sides of the elastic packing element 29 and the rigid packing element 31 in the axial direction are the axial lines 33 of the plunger 8.
Is a plane orthogonal to. The inner peripheral surfaces of the elastic packing element 29 and the rigid packing element 31 are cylindrical surfaces.

On the front end face of the reciprocating plunger 8,
A pressure is generated by dividing the driving force for moving the plunger 8 forward by the area of the front end face of the plunger 8. This pressure is increased in accordance with the driving torque of the crank mechanism, that is, so-called ultra-high pressure. During one reciprocation of the plunger 8, the fluid thus pressurized is discharged from the discharge port belonging to the discharge side valve device 18 as shown in FIG.

The liquid thus discharged is cement milk composed of cement particles, cement fine particles and water. As shown in FIG. 3, a minute gap (exaggerated in the figure) S is positively provided between the high-hardness cylindrical body 22 and the rigid packing element 31.

The pressure in the gap S is a high pressure P. The pulsating pressure of the pump chamber 14 shown in FIG. 2 is transmitted to the gap S with almost no pressure drop.
Approximately equal to the high pressure of Fine particles of cement enter the gap S. As shown in FIG. 2, the compressive force of the inner portion of the elastic packing element 29 acts between the elastic packing element 29 and the high-hardness cylinder 22 on the elastic packing element 29 and the high-hardness cylinder 22. are doing. However, as shown in FIG. 3, when the high pressure P is higher than the compressive force, a small but minute gap is formed between the inner peripheral surface of the elastic packing element 29 and the outer peripheral surface of the hard cylinder 22. Occurs.

The minute gap gives a large resistance to the flow of the fluid that is going to pass through the minute gap. Therefore, the pressure of the liquid flowing downstream (left side in FIG. 3) passing through the minute gap causes a large head drop, and the pressure of the passing fluid drops to a considerably low pressure on the low pressure side.

In the past, regarding the actual machine using the U-packing 01 shown in FIG. 7, the phenomenon that the outer peripheral surface of the plunger 02 facing the inner surface of the U-packing recently occurs in response to an inquiry from a user is successive. It became clear that it was. There is no correspondence between the generation of the scratch and the liquid leakage, and the problem caused by the presence of the U packing is not derived. Conversely, this U
The actual machine without the packing is more resistant to liquid leakage than the one with it.

Fine particles of cement milk (cement particles)
Has a hardness corresponding to various ceramic particles, and is higher than the hardness of the highest hardness metal shrink-fitted around the plunger. The U packing which is pressed inward in the radial direction under high pressure or ultra high pressure and pressed against the metal surface, and the cement particles sandwiched between the metal upper surfaces have the same polishing action as a paper file for polishing metal. The cause factors related to the durability of the packing are softening due to heat generation of the packing and wear of the plunger, but it has not been well known until now which factor the actual decrease in sealing performance is based on.

Conventionally, when the sealing performance is deteriorated, means for tightening the packing in the axial direction to increase the pressure contact force between the gland packing (a packing group including V packings provided on the rear side of the U packing, that is, on the low pressure side) and the plunger. Was taken. According to such a means, the plunger is heavily burdened also in the first half of use, and the wear between the gland packing and the plunger, which is tightened more and more in the second half, is further promoted. The high-hardness alloy normally used for plungers is not a material that will cause scratches when attempting to scratch it artificially.

The fact that extremely small mineral cement particles having a diameter of about 0.03 mm penetrating between the packing and the plunger which are strongly fastened actually damages the surface of the plunger means that the cement particles are equivalent to the cement particles. Means that it is pressed against the plunger with strong pressure. The pressing force is a combined force of the tightening force for tightening the packing and the pressure of the liquid acting on the packing.
It is almost certain that it is presumed that the cement particles receiving such a combined force from the packing wear the plunger. The conventional pump has fallen into a vicious cycle in which such liquid leakage and further tightening to cope with the leakage are repeated.

The elastic packing element 29 and the rigid packing element 31 of the packing group shown in FIG. 3, which is an embodiment of the packing according to the present invention, both have side surfaces (surfaces at which straight lines directed in the axial direction intersect) perpendicular to the axis. And the pressure P does not become an action force for positively pressing the elastic packing element 29 and the rigid packing element 31 against the surface of the plunger. Before the pump is driven, there is no gap between the elastic packing element 29, the rigid packing element 31, and the surface of the plunger. Before the pump is driven, the elastic packing element 29 and the rigid packing element 31 fastened by the packing holder 24 shown in FIG. 2 are compressed in the axial direction and slightly expanded in the radial direction, and a certain pressure P 'Presses against the plunger surface.

When the pump is driven, the pressure P is increased on the front side (pump chamber side) of the elastic packing element 29 and the rigid packing element 3.
1 acts on the elastic packing element 2
9. Acts on the inner peripheral surface of the rigid packing element 31 to act radially outward (radially). If P> P ', the elastic packing element 29 and the rigid packing element 3
A gap is formed between the plunger 1 and the plunger surface, and the cement liquid enters the gap. The liquid flow leaking from the narrow gap under the pressure P forms a jet flow, and in a narrow area, the strong turbulent flow causes a wedge effect, and the leakage is suppressed on the contrary. The cement particles in this leak stream do not wear the plunger.

The pressure of this leakage flow sharply drops, and drops to a pressure P ″ which is extremely weaker than the pressure P. The elastic packing element 29 and the rigid packing element 31 on the rear side exert a tightening force. With a correspondingly high pressure on the plunger, the weak pressure P ″ can no longer actively create a gap between the elastic packing element 29, the rigid packing element 31 and the plunger surface. For this reason, wear to some extent due to cement particles occurs,
When the abrasion occurs, the pressing force is reduced, and a gap is eventually formed. Since the pressure P ″ in the gap is extremely weaker than the pressure P, even if the cement particles are pressed against the plunger without forming a gap, the problem of wear is no longer present. The higher the discharge pressure of the pump, the less influence it has on the decrease in the discharge pressure.

In the packing device of the plunger type pump according to the present invention on the premise of leakage, the leaked liquid passes through the collecting peripheral groove 27 and the collecting plug 28 of the leaking liquid collecting ring 26 shown in FIG. It is returned to the suction side of the pump. It is only necessary to connect the collection plug 28 to the suction line by a tube. To this end, the liquid in the collection plug 28 is drawn by the fluid in the suction side conduit and is sucked into the pump chamber.

As shown in FIG. 4, the leak liquid recovery ring 2
The fresh water in the flow path 41 leading to the collecting circumferential groove 27 of No. 6;
It may be discharged. It is advantageous to introduce a water-soluble lubricating oil in this, because the cement particles between the packing and the plunger can be washed away. Further, the leaking liquid can be completely suppressed in the flow path system by the auxiliary packing 32 which is a U packing. Since only the atmospheric pressure acts on the auxiliary packing 32, there is no problem of wear.

FIG. 5 shows another embodiment of the elastic packing element 29 or the rigid packing element 31. Hereinafter, the case of the elastic packing element 29 will be described.
The vector P of the pressure of the liquid acting on an arbitrary point on the outer surface of the part close to the sliding part is directed outward with respect to the center line of the plunger. The pressure P does not press the elastic packing element 29 against the peripheral surface of the plunger 8. The outer surface 29a of the elastic packing element 29 does not necessarily need to be formed on both sides. High pressure side outer surface 29a
It may be formed only.

FIG. 6 shows still another embodiment of the elastic packing element 29. The vector P of the pressure of the liquid acting on an arbitrary point on the outer surface of the portion close to the sliding portion is directed inward with respect to the center line of the plunger. The pressure vector P is oriented in a direction in which the elastic packing element 29 is pressed against the peripheral surface of the plunger 8. If the angle between the vector perpendicular to the axis perpendicular to the axis of the plunger 8 and the vector P is θ, the pressing force Pr is Pcos (θ).

If the angle θ is 90 degrees, the elastic packing element 29 matches that of the embodiment of FIG. As shown in FIG. 6, the value of cos (θ) is half at an angle θ = 60 degrees. When the angle θ is between zero and 60 degrees, the pressing force Pr does not decrease so much. However, when the angle θ exceeds 60 degrees and increases, the pressing force Pr sharply decreases. Therefore, when the angle θ is larger than 60 degrees, the operation and effect of the present invention are more advantageously exhibited. The area where the angle is a problem is an area or a part close to the plunger 8, that is, a part closer to the sliding part sliding on the plunger. The outer surface 29a of the elastic packing element 29 does not necessarily need to be formed on both sides. It may be formed only on the outer surface 29a on the high voltage side.

[0048]

The packing device of the plunger type pump according to the present invention can extend the life of both the plunger and the packing and does not reduce the discharge pressure of the pump.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a packing device for a plunger type pump according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of FIG. 1;

FIG. 3 is a sectional view showing a pressure action of a packing device of a plunger type pump according to the present invention.

FIG. 4 is a sectional view showing another embodiment of the packing device of the plunger type pump according to the present invention.

FIG. 5 is a cross-sectional view showing another embodiment of the elastic packing or the rigid packing according to the present invention.

FIG. 6 is a sectional view showing still another embodiment of the elastic packing according to the present invention.

FIG. 7 is a sectional view showing a conventional U packing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 8 ... Plunger 6 ... Main body casing (cylinder) 15 ... Suction side valve device 22 ... High-hardness cylindrical body (plunger) 23 ... Front side packing presser 25 ... Packing group 26 ... Leakage liquid recovery ring 27 ... Recovery peripheral groove 28 ... Plug for recovery 29 ... Elastic packing element 31 ... Rigid packing element

Claims (9)

[Claims] 1. A mineral comprising: a plunger; a cylinder for sliding the plunger in an axial direction of the plunger; and a packing group including a packing element inserted into a sliding portion between the plunger and the cylinder. A packing device of a plunger type pump used for a plunger type pump for increasing the pressure of a liquid containing particles, wherein the group of packings is a liquid pressure acting on an arbitrary point on an outer surface of a portion close to a sliding portion in a radial direction. And a packing element directed outward with respect to the center line of the plunger. 2. The packing device for a plunger type pump according to claim 1, wherein the outer surface of the packing element is formed at least on a high-pressure side in the axial direction of the sliding portion. 3. A mineral comprising: a plunger; a cylinder that slides the plunger in the axial direction of the plunger; and a packing group including a packing element inserted into a sliding portion between the plunger and the cylinder. A packing device of a plunger type pump used for a plunger type pump for increasing the pressure of a liquid containing particles, wherein the group of packings is a liquid pressure acting on an arbitrary point on an outer surface of a portion close to a sliding portion in a radial direction. When the angle of the vector goes inward with respect to the center line of the plunger, and the angle between the vector and a plane orthogonal to the center line is represented by θ, a plunger type including a packing element satisfying θ> 60 degrees Pump packing device. 4. The packing device for a plunger type pump according to claim 3, wherein the outer surface of the packing element is formed at least on a high pressure side in the axial direction of the sliding portion. 5. The packing device for a plunger type pump according to claim 3, wherein the angle θ is constant. 6. The packing device for a plunger type pump according to claim 4, wherein the angle θ is 90 degrees. 7. A mineral comprising a plunger, a cylinder for sliding the plunger in the axial direction of the plunger, and a packing group including a packing element inserted into a sliding portion between the plunger and the cylinder. A packing device for a plunger type pump used in a plunger type pump for increasing the pressure of a liquid containing particles, wherein a side surface of an outer surface of a part close to a sliding part in a radial direction is orthogonal to the axis. A packing device for a plunger-type pump. 8. The packing device for a plunger type pump according to claim 7, wherein the portion near the sliding portion is a portion on the high pressure side in the axial direction. 9. A packing device for a plunger type pump according to claim 1, wherein the leaking liquid is returned to a suction side of a pump chamber.